Attempts to make phosphate glasses in a chemically stable form by methods employed in the prior art have been largely unsuccessful. Typical of such prior art systems in which phosphates are employed are those processes set forth in U.S. Pat. Nos. 2,434,281; 2,031,579; 2,064,344 and 3,485,646. The compositions utilized in those patents include P.sub.2 O.sub.5 or H.sub.3 PO.sub.4 or HPO.sub.3. Compounds which decompose to the oxide to form a compound such as NaPO.sub.3 and Al(PO.sub.3).sub.3 have also been prepared from HPO.sub.3 which are then used to prepare the glass. However, the prior art techniques do not recognize the criticality in obtaining a glass product of desired properties by preparing precursor compounds, to be melted to form the glass, in essentially pure stoichiometric monobasic form prior to melting the compounds. Also, no known prior art system appears to recognize the criticality of reacting the precursor monobasic compounds in a thermal process to obtain a melt which is further reacted to form stable phosphate glasses when appropriately cast and annealed. Moreover, there is no recognition in the prior art of the importance of restricting the glass composition to a single phase in order to achieve complete polymerization with consequent high resistance to hydrolysis in boiling water.